According to BOLT 11:
- after the `timestamp` plus `expiry` has passed
- SHOULD NOT attempt a payment
Add a convenience method for checking if an Invoice has expired, and use
it to short-circuit payment retries.
When a payment fails, it's useful to retry the payment once the network
graph and channel scores are updated. InvoicePayer is a utility for
making payments which will retry any failed payment paths for a payment
up to a configured number of total attempts. It is parameterized by a
Payer and Router for ease of customization and testing.
Implement EventHandler for InvoicePayer as a decorator that intercepts
PaymentPathFailed events and retries that payment using the parameters
from the event. It delegates to the decorated EventHandler after retries
have been exhausted and for other events.
